Synthesis of helical aluminium catalysts for cyclic carbonate formation.

Helical aluminium complexes [Al2X4(μ-nbptam)] (X = Me 1, Et 2), [Al2X4(μ-fbpam)] (R = Me 3, Et 4), [Al3X7(μ-nbptam)] (X = Me 5, Et 6) and [Al3X7(μ-fbpam)] (X = Me 7, Et 8) have been prepared by treatment of scorpionate ligand precursors with two or three equivalents of the corresponding trialkylaluminium derivative. The structures of these complexes have been determined by spectroscopic methods and the X-ray crystal structure of complex 1 has also been established. These complexes have been studied as catalysts for the chemical fixation of carbon dioxide into cyclic carbonates displaying good catalytic activity. When cyclohexene oxide was used as a substrate, polyether-polycarbonate was obtained in a ratio which is highly dependent on the cocatalyst and the catalyst to cocatalyst ratio used.